“Sloughing” of metal-organic framework retaining nanodots via step-by-step carving and its flame-retardant effect in epoxy resin

Hollow nanocages derived from metal-organic frameworks (MOFs) feature more exposed active sites, stronger interactions, and better compatibility within the polymer matrix than solid blocks. Nevertheless, the preparation always requires the sacrifice of MOFs as a self-template. Herein, using step-by-step carving in the sequence of organic phytic acid and inorganic boric acid, MOFs can be retained in the form of nanodots with high-energy plane decorated on the hollow shells, endowing the hybrid superstructure product (ZNs-B/CP) with a relatively high surface area and enhanced catalytic properties. Owing to the ingeniously designed chemical composition and nanostructures, a load of 2 wt% ZNs-B/CP into epoxy resin improved the limiting oxygen index to 28.4% and decreased the peak of heat release rate and total heat release by 43.1% and 11.9%, respectively, assisted by the fast char formation mechanism, with slight influence on the mechanical strengths of the composites. Under the background of burgeoning investigations for MOFs, this work supplements a feasible synthetic artifice for MOF nanodots and proposes a potential application as a flame retardant for epoxy resin.